Method of installing subsurface barrier

ABSTRACT

Systems, components, and methods relating to subterranean containment barriers. Laterally adjacent tubular casings having male interlock structures and multiple female interlock structures defining recesses for receiving a male interlock structure are used to create subterranean barriers for containing and treating buried waste and its effluents. The multiple female interlock structures enable the barriers to be varied around subsurface objects and to form barrier sidewalls. The barrier may be used for treating and monitoring a zone of interest.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/813,810, filed Mar. 30, 2004, entitled SUBSURFACE MATERIALSMANAGEMENT AND CONTAINMENT SYSTEM, COMPONENTS THEREOF AND METHODSRELATING THERETO, which is a divisional of U.S. Pat. No. 6,758,634,granted Jul. 6, 2004, which claims the benefit of U.S. ProvisionalApplication No. 60/267,320, filed Feb. 6, 2001, entitled SUBSURFACEMATERIALS MANAGEMENT AND CONTAINMENT SYSTEM, which is incorporatedherein by reference in its entirety. Furthermore, this application is acontinuation-in-part of U.S. application Ser. No. 09/729,435, filed Mar.12, 2001, entitled ADVANCED CONTAINMENT SYSTEM, which is incorporated byreference herein in its entirety.

GOVERNMENT RIGHTS

The United States Government has rights in the following inventionpursuant to Contract No. DE-AC07-99ID13727 and Contract No.DE-AC07-05ID14517 between the U.S. Department of Energy and BattelleEnergy Alliance, LLC.

FIELD OF THE INVENTION

The present invention relates generally to methods, components andsystems for in situ containment and management of buried waste,contaminated media, and their associated components. Also these methodsand devices can be utilized for resource recovery. More particularly,embodiments of the present invention relate to an improved barrier, aswell as to its installation and use, for reliably containing andmanaging leachate, gas phase contaminants, and the like, originatingfrom a zone of interest.

BACKGROUND

Containment, management, and disposal of various types of waste arelong-standing problems. Early waste management and disposal systems wereprimitive, as there were few or no disposal or environmental regulationsin place at the time. In countless instances, the waste was simplyburied underground. The volume of waste that has been buried istremendous. Some experts estimate that landfills in the United Statesalone hold more than 3 million cubic meters of buried waste. Further,much of the waste that was buried comprises heavy metals such as mercuryand cadmium, carcinogenic materials such as trichloroethylene,radioactive materials, and other hazardous substances.

While burial and similar approaches produced an aesthetically pleasingresult by removing the waste from sight, it was soon discovered thateffluent from the buried waste was working its way through the soil andinto the groundwater. This process is commonly known as leaching.Because groundwater is a major source of water for drinking and foragriculture, contamination of the groundwater by leaching is a majorconcern.

The contamination caused by buried waste is not limited solely togroundwater however. At least some of the contaminated groundwater findsits way into waterways such as streams, rivers, and lakes, thuspolluting those waterways and poisoning the plant and animal life.Obviously, polluted waterways pose a threat to humans as well,particularly in the case of waterways and bodies of water used forrecreational purposes and/or as a source of drinking water.

Not all of the cases of groundwater pollution arise from the leaching ofchemicals from waste sources. In some cases, the waste is buried in thepath of the groundwater, and as groundwater flows through the waste, itcollects various chemicals and toxins from the waste and deposits thosechemicals and toxins in other soils and waterways.

While many of the problems associated with buried waste concern theeffect of leachate on groundwater, buried waste also typically emits gasphase contaminants that must likewise be contained and managed. Such gasphase contaminants can also pollute the soil and the groundwater, andmay build up to unsafe pressures which could ultimately result inexplosion and/or atmospheric venting of the gas.

Clean soil and groundwater are important to human, plant, and animallife as well as to the environment in general. Accordingly, a variety ofmethods and devices have been devised to attempt to resolve the problemsinduced by buried waste. These remedies can be broadly grouped into thecategories of remediation and containment. Remediation remedies focus onprocesses designed to change the chemical composition of a contaminatedmaterial or contaminant to one more benign, while containment remediesseek to eliminate the pollution problem by removing or isolating thecontaminants and contaminated material from the surrounding area.

Remediation approaches such as biological treatments, thermal processesand chemical processes are problematic for a variety of reasons. Inparticular, many of these remediation techniques are expensive andpotentially hazardous. Further, it is difficult to verify theeffectiveness of many of the treatments and remediation-type approachesmay not be appropriate for all types of contaminated material. Finally,determining the proper remediation technique is, in itself, a complexand time-consuming process, particularly in view of the web ofregulations and procedures that govern such treatments.

Containment, barrier, or in situ, approaches are problematic as well.One known containment approach is simply to dig up and remove thecontaminated soil for treatment and/or disposal. This approach isexpensive and time-consuming and often accomplishes little more thanmoving the problem to another location. Other containment approachesinvolve installing vertical and/or horizontal barriers around the buriedwaste. In theory, this approach is attractive because it does notinvolve digging up or otherwise disturbing the buried waste.

However, conventional containment or barrier systems suffer from avariety of inadequacies including lack of durability, continuity andintegrity. These inadequacies are a function of numerous factorsassociated with the environment in which the containment or barriersystems are located including, but not limited to: exposure to harshchemicals such as concentrated saline solutions, and saturated calciteand gypsum solutions; exposure to extreme thermal gradients such as aretypically experienced in freeze/thaw zones; and exposure to stressesinduced by shifting in the earth.

Hydraulic conductivity, which is the rate at which a fluid or hazardoussubstance flows through a barrier, is unacceptably high in some barriersystems while other conventional barrier systems are not particularlywell-suited to a variety of soil conditions such as hard rock and sand.A further flaw is that many barrier systems do not provide methods forevaluating the integrity of the barrier during and after installation,which is complicated by the fact that many barrier systems also lackprovision for long term monitoring of the containment zone and anyleachate therefrom. The inability to monitor a barrier system that isisolating hazardous waste is unacceptable because of the potential harmthat can be caused to the surrounding environment. The lack ofdurability, continuity and integrity in known containment systems has asignificant detrimental effect on the performance of those systems andthe effectiveness of those containment and barrier systems cannot bereadily determined or evaluated.

Accordingly, what is needed are improved in situ containment systems andmethods for installing these systems. A containment system that iscapable of containing, collecting and/or processing effluent which wouldotherwise escape from a zone of interest, wherein such effluentincludes, but is not limited to, leachate, gas phase contaminants,waste, water, and any other material that is desired to be contained,collected, and/or processed would be advantageous.

BRIEF SUMMARY OF THE INVENTION

The present invention includes systems and methods relating tosubterranean containment barriers. Tubular casings having male interlockstructures and cooperative multiple female interlock recesses are usedto create subterranean barriers for containing and treating buried wasteand its effluents. The multiple interlocks allow the barriers to bevaried in placement around subsurface objects and to form barriersidewalls. The barrier may be used for treating and monitoring a zone ofinterest including contaminants.

Casing sections are interlocked to adjacent sections using the maleinterlocking structures and cooperative female interlock recesses. Asealant is disposed in the recess. Sealants may disposed prior toconnecting adjacent casing sections, or after the interlock is formed.Thermoplastic sealants may be used to enable resealing in the event of abreach by reheating to reestablish the seal.

Methods of constructing the barrier include methods for reducing theintrusion of foreign matter into the interlocks during construction byblocking, methods of collecting and containing contaminants using thebarrier structures. The components may also be used to treat zones ofinterest by removing contaminants therefrom, or introducing desiredmaterials thereinto.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective, partial cutaway view of a micro tunnelingdevice installing casing sections underneath a contaminated zone ofinterest in accordance with a first embodiment of a subterranean barrierof the present invention;

FIG. 1A is a side view of a second embodiment of a subterranean barrierin accordance with the present invention;

FIG. 1B is a side view of a third embodiment of a subterranean barrierin accordance with the present invention;

FIG. 2 is a perspective view of a first embodiment of a casing sectionin accordance with the present invention;

FIG. 3 is a front view of several alternative embodiments of casingsections in accordance with the present invention, shown as interlockedwith one another;

FIG. 3A is a back view of a portion of a male interlock structure madein accordance with the present invention;

FIG. 3B depicts some alternative embodiments of male interlockstructures in accordance with the present invention;

FIG. 4A is a front view of another embodiment of a casing section inaccordance with the present invention;

FIG. 4B is a front view of an additional embodiment of a casing sectionin accordance with the present invention;

FIG. 4C is a front view of the embodiment of FIG. 4B, modified for usein treating a zone of interest, in accordance with the presentinvention;

FIG. 4D is another front view of the embodiment of FIG. 4B, modified foruse in treating an effluent from a zone of interest, in accordance withthe present invention;

FIG. 5 is a cross-sectional view of one embodiment of an interlockrecess, in accordance with the present invention;

FIG. 6 is a front view of a section of a barrier, made in accordancewith the present invention;

FIG. 6A is a front view of a different section of a barrier made inaccordance with the present invention; present invention; and

FIGS. 7A and 7B are a schematics of a casing section having a pluralityof sensors associated therewith for monitoring the zone of interest andthe barrier.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The threat to the environment produced by buried waste begins when thecontaminants produced by buried waste leach into the groundwater. Oncegroundwater has been contaminated, the potential harm is great, becausegroundwater typically makes its way to rivers and lakes, which arefrequently sources of drinking water and irrigation water. In thismanner, the contaminants originally produced by buried waste make theirway to plants, animals and humans.

A containment system including a barrier in accordance with theprinciples of the present invention addresses these and other concernsof buried waste by isolating a containment zone of interest, whichprovides several significant advantages. The systems, methods andapparatus of the present invention are capable of creating a continuousbarrier of various sizes and configurations. The barriers can beinstalled in both saturated and unsaturated zones of interest and in avariety of geologies from soft soil to hard rock. Systems and methodsfor the verification of the barrier installation as well as structuralcontinuity of the barrier are also included within the scope of thepresent invention.

As used herein, “buried waste” refers to, without limitation:construction and demolition materials such as lumber and concreteblocks; laboratory equipment such as glassware and tubing; processequipment such as valves, ion exchange resins, and heat exchangers;maintenance equipment such as oils and greases; decontaminationmaterials such as paper, rags and plastics; hazardous and radioactivematerials; and any other type of waste or garbage which is buried in theground. The chemicals and other substances produced by buried wastewhich leach into the surrounding soil and groundwater are alsoencompassed by the term buried waste. “Zone of interest” refers to anarea or volume of earth containing buried waste. A containment system istypically designed to isolate the zone of interest from the surroundingearth and water such that the buried waste and associated leachate isgeographically confined to the zone of interest.

The present invention is described in terms of diagrams and figures.Using the diagrams and figures in this manner to present the inventionshould not be construed as limiting its scope. Rather, the diagrams andfigures are intended to be exemplary embodiments of the presentinvention. Additionally, the diagrams and figures are not necessarilydrawn to scale. It will be appreciated that other embodiments of thepresent invention are also be contemplated and such other embodimentsare within the scope of the present invention.

FIG. 1 depicts a zone of interest 100 to be isolated by a firstembodiment of a barrier 500 in accordance with the principles of thepresent invention. In order to contain zone of interest 100, a trench200 is first excavated on either side of zone of interest 100 (only onetrench is shown) containing buried waste 102. Micro tunneling device 300is then placed in trench 200. Trench 200 facilitates the placement ofmicro tunneling device 300, but the creation of trench 200 may beomitted in some embodiments. If trench 200 is excavated, the removedsoil, if contaminated, may be disposed of by appropriate and approvedmethods. Additionally, any soil excavated by tunneling device 300 alsobe collected, scanned, and disposed of by similar methods.

One type of micro tunneling device 300 is known as a micro tunnel boringmachine, or micro TBM. In a currently preferred embodiment, microtunneling device 300 comprises an auger head 302 or the like for rotaryexcavation of soil 104. However, it is contemplated that the inventivebarrier system may be installed in any of a number of different types ofsoil and rock, or combinations thereof. Accordingly, installation of thecontainment or barrier system by other excavation devices including, butnot limited to, ‘double-tube down the hole’ drills (preferred for hardsoil and soft rock), rotary percussion drills (preferred for hard rock),Multi-face Tunnel Boring Machines, Multi-face Shielded Tunnel BoringMachines, a Shielded Tunnel Boring Machine coupled with a HorizontalCutting Screw Auger, Pipe Propulsion, Curved Pipe Propulsion, TrenchCutting, and the like is contemplated as being within the scope of thisinvention. Attainable boring and installation speeds are about 50meters/day of tunnel through soft soil, about 25 meters/day of tunnelthrough hard soil/soft rock, and about 8 meters/day of tunnel throughhard rock.

In order to contain the buried waste in a zone of interest, microtunneling device 300 serially drills a plurality of parallel tunnelsunderneath the zone of interest. Preferably, each tunnel issubstantially circular in cross-section. However, this inventioncontemplates as within its scope tunnels of a wide variety of other,different cross sectional shapes. Each tunnel of FIG. 1 begins in trench200 and ends in another trench 200 (not shown) on the other side of zoneof interest 100. Micro tunneling device 300 lines each tunnel withlongitudinal adjacent casing sections 400 so as to form a tube 401inside each tunnel as drilling progresses. One of the functions ofcasing sections 400 installed during tunneling is to support the portionof the tunnel already drilled behind auger head 302 or other boringhead. Casing sections 400 comprise a hollow elongated body 409 having alength defining a longitudinal axis and a perimeter around thelongitudinal axis. The body 409 may have any cross-sectional shapedesired. Casing sections 400 are optimally constructed of steel,ceramics, aggregate, polymers and other materials selected according tothe compressive strength, flexibility and corrosion resistance that isdesired or required for the resulting barrier and formed according tomethods known in the art. It will be appreciated that alternative casingmaterials may be selected and used in order to provide proper protectionand containment for differing types of waste, the collection orcontainment of other substances, or the support of other structures.Casings 400 may include a corrosion resistant coating, such as an epoxy,a polymer such as, polytetrafluoroethylene (Teflon® polymer), bondedceramic or polymers, to extend their useful lives. In one exemplaryembodiment, each casing section 400 may be about 0.5 meters in diameterand in the range of about 50 meters to about 150 meters long.

FIG. 1A illustrates a second embodiment of a barrier 500A used tocontain a zone of interest. In the FIG. 1A embodiment, a single trench200A is excavated on one side of the zone of interest 10A. This may bedone where desired, or where a subsurface object 201 prevents theplacement of a second trench 200A. The barrier 500A is formed by boringlaterally adjacent tunnels and lining with casing sections 400 asdescribed previously herein, only the barrier is formed by running thecasing sections 400 from the surface S to the single trench 200A.

FIG. 1B similarly illustrates yet another embodiment of a barrier 500Bthat may be used to contain a zone of interest 100B. A central tunnel202 is bored beneath the zone of interest. Two trenches 200B areexcavated on opposite sides of the zone of interest 100B substantiallyparallel to central tunnel 202 and casings 400B are placed in laterallyadjacent tunnels bored from each of the trenches 200B to the centraltunnel 202, forming barrier 500B. A single section of casing 400 may beused for each trench-to-tunnel span, enabling barrier 500B to be formedwithout end to end joints between casing sections 400B. Central tunnel202 may be used to collect leachate from certain embodiments of abarrier 500B, as will be discussed further herein, or for othermonitoring and maintenance of the system.

FIG. 2 illustrates one embodiment of casing 400 including complementaryinterlocking structures 402A and 402B configured to interlock laterallyadjacent casing sections 400. Structure 402A is a T-shaped (in crosssection) male interlock structure disposed externally on casing section400 and running along the longitudinal axis. Each structure 402B is anexternally disposed female interlock defining a channel 405 opening intoan access slot 455. In some preferred embodiments, there are threefemale interlock structure 402Bs disposed at 90° intervals around thecircumference of casing 400 with respect to one another and to maleinterlock 402A. Complementary interlocking structures 402A and 402Bprovide multiple benefits, for example these structures may be used topositively interlock laterally adjacent casing sections 400 and, oncethe first tunnel is drilled and lined with casing sections 400, acomplementary interlocking structure 402B thereof serves to accuratelyand reliably guide complementary male interlocking structure 402A oflaterally adjacent casing sections 400 into place, thus ensuringaccurate placement and orientation of those casing sections 400, and,thus, of barrier segment 500 as a whole. Further, the multiplicity offemale interlocks 402B allows for flexibility in the interconnectionsbetween casing sections 400, which will be discussed in further inconnection with FIGS. 5 and 6. Once in position, the central bore 403 ofa casing 400, and any space or volume within the female interlockstructure 402B not occupied with male interlock 402A may be filled witha sealant such as grout or bentonite to provide further impermeabilityto the barrier 500, as will be discussed further below.

FIG. 3 depicts several embodiments of casings 400 shown laterallyinterconnected to form a section of a barrier 500 that may be used inaccordance with the teachings of the present invention. Casing 400Aincludes a generally T-shaped (in cross section) male interlock 402Adisposed on the external surface of the casing 400A and running along alongitudinal axis thereof. Casing 400A further includes one or morefemale interlock structures 402C, formed as an internal channel 404accessible from the external surface of the casing 400A through accessslot 455. As barrier 500 is formed by interlocking laterally adjacentcasings 400A, the interlock space between the external surface of eachcasing 400A body is reduced or eliminated by the receipt of maleinterlock structure 402A in channel 404, allowing for a stronger barrier500 to be formed.

A number of bleed slots 405 may be formed in the wall of internalchannel 404. If a sealant, such as grout or bentonite is injected intothe central bore 403, it may pass through the bleed slots 405 into theinterlock space allowing both bore 403 and the interlock volume to befilled and sealed in one operation. A portion of the casings 400A may beconstructed of a semipermeable material such as a porous ceramic thatallows air to pass therethrough. As the central bore 403 is filled withsealant, displaced air exits the casing 400A through the semipermeablematerial, which then becomes impermeable due to the filling of the porestherein with sealant. This reduces the problem of voiding and bubblesduring sealant, such as grout, injection.

One potential problem with the emplacement of casing sections is theintroduction of extraneous material, such as dirt or debris, into thechannels of female interlock structures 402B and 402C which dirt ordebris may prevent entry of a male interlock structure 402A. Techniquesfor reducing this problem are included within the scope of the presentinvention. Casing 400B includes a frangible seal 406 located over theexternal openings of the female interlock structures 402C. Frangibleseal 406 may be constructed of any suitable material, such as a ceramic,aggregate, thin section of frangible metal, a membrane (such asneoprene) or a selectively permeable material that may aid in using thecasing for treating the zone of interest 100 (where the channels offemale interlock structures 402B or 402C are not used for the interlockitself). As the casing 400B is emplaced, the frangible seal preventsforeign material from entering the female interlock 402C. As an adjacentcasing, 400B is emplaced, the male interlock structure 402A thereof isinserted through access slot 455 down the length of female interlockstructure 402B. The frangible seal 406 is broken, displaced, or cut bythe male interlock, which may be assisted by a sharpened or slantedleading edge 411, such as that shown in FIG. 3A.

It will be appreciated that frangible seal 406 may include a seal, suchas a neoprene membrane may be placed over the access slot 455. As theseal 406 is cut by the sharpened leading edge, it remains in place toform a seal between the female interlock structure 402B and the insertedmale interlock structure 402A. This seal allows the enclosed volume ofthe bore 403 and interlock to be known, as leakage is preventedtherefrom during filling. The volume of sealant injected therein may bemeasured to determine if voiding or other variances are occurring thatmay reduce the effectiveness of the barrier 500 and appropriatecorrective measures taken.

Another technique for dealing with the problem of foreign material isillustrated by casing 400C. Female interlock structure 402D is filledwith a sealant, such as a soft grout 410. As the casing is emplaced,foreign material is unable to enter the prefilled female interlock 402D.As an adjacent casing, 400C is emplaced, the male interlock structure402A thereof is inserted through access slot 455 down the length offemale interlock 402D. The sealant, such as soft grout 410, is displaced(which may be assisted by sharpened or slanted leading edge 411 shown inFIG. 3A, it will be appreciated that this process may be furtherassisted by the slanted leading edge 413 on the head 462 of the maleinterlock structure). A seal between adjacent casings 400C is thusformed by the interlocking. Displaced grout 410 may at least partiallyexit the female interlock 402D around the male interlock and remainthereon, creating a further seal.

FIG. 3B depicts a number of different head 462 and neck 464 embodimentsthat may be used for male interlock structure 402A. It will beappreciated that any structure that is capable of being slidablyinserted down the channel 404 through access slot 455, to residetherein, that may not be laterally removed from may be used. Embodimentswhere the enlarged head 462 is angled outwardly may be used toeffectuate an improved seal by contacting the channel 404 wall whenforce is applied in a laterally separating direction to the barrier500B.

FIG. 4A illustrates another embodiment of a casing 400D made inaccordance with the principles of the present invention. Casing 400Dincludes four female channels 422, three of which are used to form thefemale interlock structures 402E in connection with an access slot 455.A central chamber 420 is formed between the female channels 422, eitherby the inner walls 423 thereof, or as a separate structure. Integralgrout injection manifolds 424 are formed by the sidewalls 427 of thefemale channels 422 and the outer wall 429 of the casing 400D. Sealantmay be injected into an appropriate manifold 424 and flow through bleedslots 405 into the interconnect structure volume in order to form animpermeable seal between adjacent casings 400D. Where a female channel422 is prefilled with a sealant, such as a soft grout, the sealant mayflow out of the channel 422 into a manifold 424 through the bleed slots405 as it is displaced by the male interconnect 402A. This allows animpermeable seal to be formed between adjacent casings 400, withoutrequiring the entire casing to be filled with a sealant or without theneed for constructing separate grout injection manifolds. Alternatively,grout channels 407 located on the external surface of a casing 400D maybe used to direct sealant flow over the surface of the casing 400D tocreate an additional sealing layer atop the barrier 500. Of course, itwill be appreciated that grout flow openings 409 may be made directly inan external surface of a casing 400, allowing sealant injected thereinto flow through and for this additional sealing layer.

FIG. 4B illustrates another embodiment of a casing 400E made inaccordance with the principles of the present invention. Casing 400Econtains an internal tube 440, which may be a square tube. Maleinterlock 402A is attached on the external surface of the casing 400E,as with the other embodiments discussed herein. Female interlocks 402Fare formed by the longitudinal access slots 455 down the length of thecasing 400E and internal chambers 441 created by the space between theinternal tube 440 and the external wall of the casing 400E.

Casing embodiments similar to those depicted as 400D and 400E may easemanufacturing as they are capable of construction with all weldingperformed external to the pipe. For example, the internal tube 440 orcentral chamber and 420 and female channels 422 may be constructed bywelding flat pieces to form the desired shapes. Additional pieces maythen be welded to the internal structures to form the external surfaceof the casing 400. Where the curved pieces are used, accurate jigs maybe utilized to maintain proper positioning. This allows the labor costassociated with the construction of a casing to be reduced, as well aseliminating a need for specialized welding tools to operate within theinterlocks. It will, of course, be appreciated that internal structuresmay be formed by a suitable method, such as welding, and then slidablyinserted down into a casing 400 and welded of other wise bonded thereto,whereupon access slots 455 may be cut into the external surface of thecasing 400.

Casing embodiments that feature a central chamber 420 or internal tube440 also add another level of flexibility for monitoring undergroundconditions and remediation. FIG. 4C illustrates a casing 400E adaptedfor such a purpose. Internal tube 440 and the internal chamber 441B usedfor interlocking with another casing 400 are filled with sealant 442 toprovide an impermeable barrier. The topmost internal chamber 441A isleft unfilled. The longitudinal access slot 455A is open to allow liquidor gaseous effluent to flow therein (either left open or covered by apermeable material). Effluent flows from the zone of interest throughopening 455A into internal chamber 441A. The effluent may then flowthrough internal chamber 441A down the casing 400E (which may be sloped)to be collected for filtration, monitoring or other purpose. Where thebarrier 500 includes a central tunnel 202, as in the embodiment shown inFIG. 1B, effluent may be collected and processed therein, or flow to thetunnel 202 and continue to flow therethrough to a collection location.The lower internal chamber 441C may be used for monitoring the barrier500 and casing 400 integrity, as will be discussed further herein. Theremaining internal chamber 441D (or any other unused chambers) may befilled with sealant to provide additional structural support orprotection to the barrier 500.

As illustrated by FIG. 4D a casing 400E, may include reactive sectionsor components to extend barrier life, provide maintenance, or serve topretreat materials that pass through selectively permeable portions ofthe barrier 500. Longitudinal access slot 455A is open to allow leachate(shown as arrow 108) or other liquid or gas effluent to flow therein tothe topmost inner chamber 441A of a casing 400E of FIG. 4D. One or morelayers of reactive material are contained in internal tube 440. Theeffluent is allowed to flow into the internal tube 440, through openingsor vias 470, to contact a reactive layer 446A therein. Reactive layer446A targets certain contaminants, either by filtration, or by reactingtherewith. A plurality of layers 446A, B. C. etc. may be used toselectively treat a number of different contaminants, sequentially. Thelayers 446A, B. C. etc. may be formed as reactive trays or barrier slugsthat can be removed and replaced from the barrier as the reactive layer446A is exhausted, or to target different contaminants at differentareas of the barrier.

Once the effluent has passed through the reactive layers, it may beallowed to exit the casing through bottom longitudinal opening 443C(again through opening or vias, not shown), or it may flow along thefloor of internal tube 440, or lower internal chamber 441C (where lowerlongitudinal opening 455C is sealed) to a collection point, such ascentral tunnel 202 (see FIG. 1B). A number of different reactive layers446 may be placed along the axis of a casing 400, such that a desiredtreatment series is encountered by an effluent flowing down a reactivecasing 400. It will be appreciated that the barrier 500 may thus be usedto contain collect and treat gas phase contaminants that pass through oremanate from the zone of interest. A vacuum may be applied through aselectively permeable wall of a casing 400 to extract gas phasecontaminants. Conversely heat, chemical materials or biological agentsmay be delivered to a zone of interest through a selectively permeablewall of a casing 400. Combinations of active reactive treatments andreactive layers may be used to provide comprehensive treatment to a zoneof interest.

As seismic activity occurs, the barrier 500 may shift, settle orotherwise move. It may therefor be advantageous to provide mechanisms toaccommodate slight movements of casings 400 to occur without breakingthe continuity of the barrier 500, or to facilitate repair thereof.Where casing 400 sections are welded together, movement may requirerewelding any broken seals. FIG. 5 illustrates several methods forsealing an interlock space that can reduce the need to resort to suchmeasures.

Male interlock 402A is at least partially embedded in sealant 460 toform an impermeable seal within the interlock space 462. Sealant 460 maybe a material with a degree of elasticity that allows for some movementof the male interlock 402A with respect to the interlock space 462. Forexample, bentonite, waxes, rubbers, polysiloxane and polymeric sealantsmay provide a seal that tolerates some movement of the embedded maleinterlock 402A, without breaking the impermeable seal. Leavingadditional space free of sealant in the interlock space 462 improves theability for these elastic sealants to a maintain a seal. Some of thesesealants 460, such as the thermoplastic polymers may also possess adegree of “self-healing” ability being able to slowly flow or move torecreate a breached seal without further intervention.

Where sealant 460 is a thermoplastic material, such as wax or athermoplastic polymer, sealant 460 may be placed in the interlock space462 prior to the emplacement of the casing 400 into the barrier 500.Sealant 460 may be conformed around the periphery, or in a portion, ofthe interlock space 462 to allow the male interconnect 462 to beinserted therein without interference. Heat may then be applied tosoften the thermoplastic sealant, causing it to flow into place,creating an impermeable seal between adjacent casings 400. If theimpermeable seal is later breached by seismic activity or anotherphenomenon, that does not damage the casings 400, the sealant may bereheated, causing it to reflow and reestablish the impermeable seal.Heat may be applied in any suitable manner, such as by pumping heatedair or steam into the central bore 403 or central tube 440 of a casing400 or by heating the casing 400 in the instance it is constructed ofthermally conductive materials.

Where a more traditional sealant 460, such as grout or bentonite clay,is used, a specialized repair apparatus, such as a remote controlledrobot that fits inside a casing 400, may be moved to the location of anyvoid. Repairs may then be effected by filling the void with additionalsealant, similar to the process of dental filling.

The multiple female interconnects 402B, 402C and 402D of the casings ofthe present invention provide additional flexibility in assembling abarrier 500. For example, where a barrier is placed in an area thatlimits the ability to recover a failed auger head, boring head or drillbit, such as a around a zone of interest that contains radioactivematerial, or where the cost of recovering an auger head, boring head ordrill bit or replacing a failed casing 400 are high, the barrier 500 maybe constructed by working around the failed section, as depicted in FIG.6. Casing section 400A has experienced a failure, such as broken drillbit. Rather than attempt to extract and reinsert the casing 400A, casing400C is emplaced underneath the prior casing 400B, interlocked into thebottommost female interlocking structure thereof. Adjacent casingsection 400D is emplaced interconnected to casing 400C, directlyunderneath the failed casing 400A. Two more casing 400E and 400F aresimilarly interconnected from casing 400D to complete the work around.The barrier 500 is thus completed without the need to spend time andequipment repairing or recovering the failed casing 400A.

The multiple interconnect directions of the casing of the presentinvention may also be used to create barrier walls, such as laterallystepped barrier wall 502 of FIG. 6A and longitudinally stepped barrierwall 504 of FIG. 6B, in order to contain a zone of interest, eliminatingthe need for other subterranean containment structures. The work aroundand stepping ability also allow the casings of the present system to beused to create irregularly shaped barriers around underground objects.

Turning to FIGS. 7A and 7B, a ‘smart’ casing section 400G iscontemplated that incorporates a variety of sensors for monitoring thezone of interest and/or the integrity of the barrier 500. These sensorsmay be internal or external as desired. With reference first to externalsensors, contaminant presence/concentration sensor 606 is recessed inexterior surface 608 of smart casing section 400A and measures both thetypes and concentration of contaminants, whether present in leachate 106or in soil 104. In similar fashion, distribution sensor 610 is recessedin exterior surface 608 of smart casing section 400G and measures thespatial distribution of contaminants 108 and/or leachate 106 in soil104. Likewise, radiation detection and measurement (‘RDM’) sensor 612 isrecessed in exterior surface 608 of smart casing section 400G andmonitors and reports radiological activity in zone of interest 100. Inone embodiment, presence/concentration sensor 606, distribution sensor610, and RDM sensor 612 are installed on smart casing section 400G inlocations remote from complementary interlocking structures 402A and402B (or 402C, 402D etc).

In addition to their respective sensing functions,presence/concentration sensor 606, distribution sensor 610, and RDMsensor 612 may be configured to feed data to real-time data managementsystem 614 for processing and analysis. Real-time data management system614 may be a computer system integrating hardware, software, sensoroutput, positioning information and data analysis functions.

A variety of different sensor types are contemplated as being suitablefor performing the functions of contaminant presence/concentrationsensor 606, distribution sensor 610, and RDM sensor 612. In particular,the function of contaminant presence/concentration sensor 606 may beperformed by a surface acoustic wave (SAW) sensor or solid state sensorsuch as a field effect transistor (FET), as well as by Fourier transforminfrared spectrometry (FTIR), time domain electromagnetics, or the like.Time domain electromagnetics, which measure presence, location, andconcentration of contaminants by measuring conductivity and dielectriccontrasts of the medium in which they are located, are also suitable forperforming the spatial distribution measurement function of distributionsensor 610. The radiation detection and measurement functions of RDMsensor 612 may be performed by gamma-ray spectrometry, plasticscintillators, scintillating fibers, miniature chamber detectors, or thelike. Note that this invention contemplates as within its scope variousother types of sensors that will provide the functionality describedherein.

As indicated in FIGS. 7A and 7B, smart casing section 400G may alsoinclude a variety of internal sensors for performing a number ofdifferent functions. Because these sensors are internal to smart casingsection 400A, they may permit monitoring of various aspects of theinstallation while the installation is in progress. In view of the factthat joints between longitudinally successive casing sections 400represent a potential leak-through path for leachate 106 andcontaminants 108, the integrity of those joints is of particularconcern. Accordingly, joint integrity sensor 618 evaluates the integrityof the joint between a smart casing section 400G and longitudinallyadjacent casing sections 400. That is, joint integrity sensor 618determines whether there are cracks, voids, or other defects in theintercasing joint that could permit leak through of leachate 106 and/orcontaminants 108, and joint integrity sensor 618 also detects the onsetand growth of cracks and voids in the intercasing joint. As withpresence/concentration sensor 606, distribution sensor 610, and RDMsensor 612, joint integrity sensor 618 may be configured to feed data toa real-time data management system 614 for processing and analysis.

Joint integrity may be evaluated in any desired and appropriate way. Forexample, acoustic/ultrasonic time domain reflectometry sensors thatdetect cracks and large voids in structures such as smart casing section400G may be used. Also, known optical fiber sensors that employ fiberoptic principles to make strain measurements in a casing section 400 andthereby detect the onset and growth of voids and cracks in that casing400 may be used. Because joint integrity can be meaningfully evaluatedin a variety of different ways, any sensor type that would be suitablefor directly or indirectly measuring and evaluating joint integrity maybe used. Note also that the aforementioned sensor types are equallysuitable for evaluating the integrity of the structure of smart casingsection 400G itself, that is, they are not limited solely to jointintegrity applications.

In addition to containing sensors for evaluating the structure of casing400 and joint integrity, a smart casing section 400G may also include amigration sensor 620 for detecting migration and leakage of leachate 106and contaminants 108. A migration sensor 620 may be a sensorincorporating fiber optic coupled optical spectroscopy functionality formeasuring, for example, volatile organic compounds (VOCs) that may haveleaked through smart casing section 400G. However other migrationsensors suitable for measuring chemical migration, and emission of VOCsand the like are contemplated as being within the scope of the presentinvention. As indicated in FIG. 7, migration sensor 620 may beconfigured to feed data to real-time data management system 614 forprocessing and analysis.

Smart casing section 400G may also include one or more predictivesensors 622 for identifying failure precursors in barrier 500 or in acasing section 400G. One possible predictive sensor 622 measures changesin the dielectric permeability and/or permittivity of the barrier 500.Alternatively, predictive sensor 622 could be an electrical source andcorresponding antenna arrays (not shown) that may be used to measurechanges in resistivity of barrier 500. A change in resistivity from abaseline measurement taken at time of installation of barrier 500 wouldindicate a break.

Predictive sensors 622 may also be a sacrificial cathode or the like fordetecting conduction paths through a casing 400. Existence of aconduction path through a casing section 400 may indicate that a failureof that casing section 400 will ultimately occur. Because galvanicaction only occurs when there is a conduction path, galvanic action atthe sacrificial cathode serves to predict such failure. This willprovide further protection against corrosion. Alternatively, an externalgalvanic potential source may be provided to effect such protection. Aswith the other sensors, predictive sensor 622 may feed data to real timedata management system 614 for processing.

Using a barrier 500 that contains sensors as outlined in the precedingparagraphs, a number of tests may be conducted to assure the integrityof a barrier. For example, interlock void defects may be detected byconducting an ultrasonic or other nondestructive line scan between thewall of casing 400 and the male interlock structure 402A to verify sealintegrity by lack of void defects in the interlock sealant within thefemale interlock structure 402B, 402C, and 402D. Multiple scans may beconducted across different casing profiles. Similarly, interlock bondingdefects may be detected by conducting an ultrasonic or othernondestructive line scan between the wall of casing 400 and the maleinterlock structure 402A to verify seal integrity by lack of bondingdefects at the casing 400 wall or male interlock structure 402A surface.Casing end joints (where casing sections are joined end to end) defectsmay also be detected by conducting an ultrasonic or other nondestructiveline scan across casing end joints to verify seal integrity by lack ofvoid or bonding defects. Multiple scans may be done for each of thesetests.

Smart casings 400G may also be used to monitor a zone of interest 100for criticality. For example, where a zone of interest 100 containsfissable isotopes, these can achieve a critical state, if present insufficient quantity and concentration. Using RDMs andpresence/concentration sensors on or connected to the barrier 500, theconcentrations of such isotopes in the zone of interest may be monitoredto provide potential warnings prior to reaching a critical state.

It will be appreciated that using a barrier constructed according to thepresent invention, different treatment options may be practiced. Forexample, the flow rate of leachate or other effluent through a zone ofinterest may be controlled by restricting flow through a barrier 500.This allows the saturation rate of the zone of interest 100 (or thesaturation rate of a semipermeable portion of the barrier 500 surface)to be controlled, optimizing the treatment rate.

The present invention has been described in terms of buried waste, butthe systems and methods of the present invention have otherapplications. For instance, a barrier 500 having perforated orsemipermeable casings may be using in mining operations to collect theminerals of interest. For example, a barrier 500 may be constructed in aformation from which the mineral of interest may be leached into thecasings. When the collection of the mined material reaches apredetermined level, it is easily extracted from collectors in thecasings. Other applications include perforated barriers 500 used foragricultural purposes. For example, the water used to irrigate anagricultural area typically drains in a particular location. Acontainment barrier 500 having perforated casings can be installed inthe drainage area, acting similar to drainage tiles to direct the flowof drainage as desired. Casings 400 may also be used to stabilize earthor subterranean formations or provide structural support forconstruction of buildings, tunnels or other manmade structures, todivert groundwater, or to provide hydrological stabilization during damconstruction.

It will be apparent that details of the apparatus and methods hereindescribed can be varied considerably without departing from the conceptand scope of the invention. The claims alone define the scope of theinvention as conceived and as described herein.

1. A method of installing a subsurface barrier, comprising: emplacing afirst casing having at least one male interlock structure and aplurality of female interlock structures defining recesses adjacent to azone of interest; emplacing a second casing having at least one maleinterlock structure and a plurality of female interlock structurerecesses adjacent to said zone of interest, such that said at least onemale interlock structure of said second casing is received by at leastone female interlock structure recess of said first casing; and forminga seal between said first casing and said second casing to form acontinuous subsurface barrier.
 2. The method according to claim 1,wherein forming said seal comprises entraining a volume of athermoplastic sealant in said at least one female interlock structurerecess of said first casing section prior to the receipt of said maleinterlock of said second casing therein, and applying heat to said atleast one female interlocking recess to cause said thermoplastic sealantto flow and create a seal between said casings.
 3. The method accordingto claim 2, wherein entraining a volume of thermoplastic sealantcomprises entraining a volume of thermoplastic sealant that less thanthe volume of said at least one female interlock recess.
 4. The methodaccording to claim 2, further comprising reestablishing said seal in theevent of a breach by reheating said at least one female interlockstructure recess to cause said thermoplastic sealant to reflow andrecreate said seal.
 5. The method according to claim 1, whereinemplacing a first casing comprises, excavating a trench adjacent to saidzone of interest, and installing said first casing underneath said zoneof interest from a point adjacent to said zone on interest at a surfaceof the earth running to said trench.
 6. The method according to claim 1,wherein emplacing a first casing comprises, excavating a first trenchadjacent to said zone of interest, excavating a tunnel underneath saidzone of interest and installing said first casing underneath said zoneof interest such that said casing extends from said first trench to saidtunnel.
 7. The method according to claim 6, further comprisingexcavating a second trench adjacent to said zone of interest andinstalling a third casing underneath said zone of interest such thatsaid casing extends from said second trench to said tunnel.
 8. Themethod according to claim 6, further comprising emplacing a fourthcasing having at least one male interlock structure and a plurality offemale interlock structure recesses adjacent to said third casing, suchthat said at least one male interlock of said fourth casing is receivedby at least one female interlock structure recess of said third casing;and forming a seal between said third casing and said fourth casing toform a continuous subsurface barrier.
 9. The method according to claim1, further comprising continuing to install said barrier around saidsecond casing when said second casing is incapable of being sealed byemplacing a third casing having at least one male interlock structureand a plurality of female interlock structure recesses adjacent to saidfirst casing, such that said at least one male interlock of said thirdcasing is received by a second female interlock structure recess of saidfirst casing; and forming a seal between said first casing and saidthird casing to form a continuous subsurface barrier.
 10. The methodaccording to claim 9, further comprising emplacing a fourth casinghaving at least one male interlock structure and a plurality of femaleinterlock structure recesses adjacent to said third casing and adjacentto said second casing, such that said at least one male interlock ofsaid fourth casing is received by a female interlock structure recess ofsaid third casing; and forming a seal between said third casing and saidfourth casing to form a continuous subsurface barrier.
 11. The methodaccording to claim 1, further comprising selecting a female interlockstructure recess of said plurality of female interlock structurerecesses of said first casing to receive said male interlock structureof said second casing to shape said barrier into a desired conformation.12. The method according to claim 11, wherein selecting a femaleinterlock structure recess comprises selecting an appropriate femaleinterlock structure recess to form a barrier around a subsurface object.13. The method according to claim 11, wherein selecting a femaleinterlock structure recess comprises selecting an appropriate femaleinterlock structure recess to form a stepped barrier wall around a zoneof interest.
 14. The method according to claim 1, wherein emplacing saidfirst casing comprises sealing an access slot said casing to provide afixed volume inside at least one female interlock structure recess. 15.The method according to claim 14, wherein sealing a first edge comprisesattaching a neoprene membrane across said access slot.
 16. The methodaccording to claim 1, wherein forming said seal comprises filling saidat least one female interlock structure recess of said first casing withsealant section prior to emplacement and receiving of said maleinterlock structure of said second casing therein to displace a portionof said sealant to create a seal between said casings.
 17. The methodaccording to claim 16, wherein filling said at least one femaleinterlock structure recess of said first casing with sealant comprisesfilling said at least one female interlock structure recess of saidfirst casing with soft grout.
 18. The method according to claim 1,wherein forming said seal comprises filling said at least one femaleinterlock structure recess with sealant after the insertion of said maleinterlock structure therein.
 19. The method according to claim 18,wherein filling said at least one female interlock structure recess withsaid sealant comprises filling a chamber of said at first casing withsealant, such that sealant will flow into said at least one femaleinterlock structure recess through a slot located therebetween.
 20. Themethod according to claim 19, wherein filling said at least one femaleinterlock structure recess with said sealant comprises filling saidchamber until said sealant flows out of said recess over the top of saidsecond casing to form sealant layer thereon.
 21. The method according toclaim 18, further comprising selecting said sealant from the groupcomprising grout, wax compounds, polymeric compounds, rubbers, bentoniteand polysiloxane.
 22. The method according to claim 1, furthercomprising filling a chamber of said first casing with sealant, suchthat said sealant passes out of a permeable section of said casing untila sealant layer is formed external to said first casing.